Medical device with overmolded adhesive patch and method for making same

This application is a divisional application of U.S. Ser. No. 15/840,403, filed Dec. 13, 2017, which is hereby incorporated by reference in its entirety.

The present invention relates generally to medical devices and to methods for making such devices. In particular, but not by way of limitation, the present invention relates to an infusion set, patch pump or other on-body medical device having an adhesive patch which is secured to the medical device by an overmolding process during manufacture of the medical device or during manufacture of a portion of the medical device.

In the management of diabetes, insulin can be administered to a user on a continuous basis using a programmable infusion pump. The pump is small, portable and battery-operated, and can be worn or carried inconspicuously by the user. The pump is attached by a length of tubing to an infusion set, which is a disposable body-worn device having a skin-adhering base, a fluid connector, and a rigid needle or flexible catheter that conducts the insulin into the subcutaneous or intradermal layer of the user's skin. A flexible adhesive patch or pad on the bottom of the infusion set base allows for temporary skin attachment during the period (typically a few days) that the infusion set remains in place before it is removed and replaced for sanitary reasons.

Another type of insulin infusion device, known as a patch pump, has also come into use. Unlike a conventional infusion pump, a patch pump is an integrated device that combines most or all of the required components in a single housing and does not require the use of a separate infusion set or connecting tubing. A patch pump adheres directly to the skin, contains insulin in an internal reservoir, and delivers the insulin via an integrated subcutaneous catheter. As in the case of an infusion set, a patch pump typically includes a flexible adhesive patch on its bottom surface to allow for temporary skin attachment at the infusion site.

The flexible adhesive patch is typically made of a thin fibrous material, similar to a medical dressing, but with adhesive layers on both sides. On the skin contact side, an adhesive suitable for medical or surgical use is provided, and is covered by a removable backing layer or release liner made of silicone-coated kraft paper. The release liner is removed by the user before attaching the infusion set or patch pump to the skin. The skin contact adhesive must be sufficiently strong to secure the infusion set or patch pump to the skin, but must also allow for removal of the device without damaging the skin. On the device side, a different adhesive is used, one which provides for permanent attachment between the patch and the base of the infusion set or patch pump.

Unfortunately, the need to provide two different adhesives complicates the design and manufacture of the patch, and the selection of adhesives and patch materials is limited because not all adhesives and patch materials are compatible with each other. In addition, the manufacturing process for the infusion set or patch pump may require that the adhesive patch be dispensed from a continuous roll for handling by automated equipment. This may impose additional requirements on the types of adhesives that can be used.

In accordance with the present invention, an adhesive patch is secured to an infusion set, patch pump or other on-body medical device by an overmolding process during manufacture of the medical device, or during manufacture of a portion of the medical device, without the need for a separate adhesive. This provides a more secure connection between the patch and the medical device, and reduces the required number of adhesive layers from two (skin attachment side and device attachment side) to one (skin attachment side only), thereby simplifying the design and manufacture of the patch.

In one aspect, the present invention provides an on-body medical device comprising a molded plastic base and a flexible fibrous, textured, perforated or porous patch having a skin-contacting adhesive on one side and an opposite side overmolded with the base. In another aspect, the present invention provides a method of making an on-body medical device comprising injection molding a plastic base over a flexible fibrous, textured, perforated or porous patch in a mold cavity.

In an embodiment of the present invention, molten plastic is injected into a medical device mold cavity containing the adhesive patch during an injection molding operation, similar to the manner in which in-mold labeling is carried out with other types of products. Unlike an in-mold label, however, the adhesive patch is made of a fibrous, textured, perforated or porous material having many small interstices, openings or cavities into which the plastic material flows during the molding operation. When the plastic material cools and hardens, this creates a very strong bond between the adhesive patch and the medical device without the need for an adhesive.

Reference will now be made in detail to embodiments of the present invention, which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. The embodiments described herein exemplify, but do not limit, the present invention by referring to the drawings.

It will be understood by one skilled in the art that this disclosure is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the drawings. The embodiments herein are capable of other embodiments, and capable of being practiced or carried out in various ways. Also, it will be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless limited otherwise, the terms “connected,” “coupled,” and “mounted,” and variations thereof herein are used broadly and encompass direct and indirect connections, couplings, and mountings. In addition, the terms “connected” and “coupled” and variations thereof are not restricted to physical or mechanical connections or couplings. Further, terms such as “up”, “down”, “bottom”, and “top” are relative, and are employed to aid illustration, but are not limiting.

illustrates an insulin infusion setin accordance with an embodiment of the present invention. The infusion set comprises an introducer needle hubengaged with a base assembly. The introducer needle hubalso serves as a passive telescopic shield for the introducer needle (not shown) after it is removed. The base assemblyincludes a flexible patchmade of a flexible fibrous, textured, perforated or porous material such as nonwoven medical tape. The patch has an adhesive(visible in) on its underside, which is used to secure the base assemblyto the user's skin. A removable backing layer or release linercovers the skin-contacting adhesiveprior to use. The patch, adhesiveand release linerconstitute an adhesive patch assemblyas shown in.

illustrates a state in which the introducer needle huband base assemblyare ready to facilitate insertion of a flexible catheter(visible in) and an introducer needle (not shown) into the user. A removable needle guardcovers the catheterand the introducer needle (the latter initially received within and protruding from the catheter) prior to use.

illustrate the infusion setwith the introducer needle huband needle guardboth removed. With the further removal of the release linerand the with the catheterpenetrating into the subcutaneous skin layer, this is how the infusion setwould appear when adhered to the user's skin at an infusion site.

As shown in, the base assemblyincludes a plastic central portionthat overlies the flexible adhesive patchand is secured thereto by an adhesive on the upper surface of the patch. The plastic central portionincludes an upwardly facing fluid connectorhaving an openingthrough which insulin is delivered through a pre-slit resilient septumfrom a compatible fluid coupling (not shown) connected by flexible tubing to an infusion pump (both also not shown). The faceted shape of the fluid connectorand the recessed areabelow its upper face facilitate latching connection with the fluid coupling at discrete rotational positions, allowing the user to position the flexible tubing as desired.

The adhesive patchand release linerare formed with two sets of identical, aligned holes,and,as shown more clearly in. The holes,provide clearance for the emergence of the flexible catheteras shown in. The holes,serve as fluid passages for the injection molding process described in more detail hereinafter in connection with.

As shown inand in more detail in(in which the catheterand septumare omitted for clarity), the plastic central portionof the base assemblyis made up of two connected parts, a rigid inner hubdefining the fluid connectorand a somewhat more flexible outer disk. Both portions,are generally circular in shape when viewed from above. The outermost rimof the rigid inner hubhas a reduced thickness in which a plurality of through-holesare formed. The through-holesand the reduced thickness of the rimfacilitate bonding between the rigid inner portionand the flexible outer disk.

More specifically, the rigid inner hubis injection-molded in a first shot, and the flexible outer diskis molded in a second shot during which the molten plastic material of the outer diskflows around the rimand through the holes. The shape of the rimprovides a double overlapping joint with the material of the flexible outer disk, and the holesprovide additional bonding surface area and additional mechanical interlocking.

The flexible outer diskprovides improved comfort and mobility of the infusion set base assemblybecause it moves with the user during physical activity while minimizing contact of the rigid inner hubwith the user. The flexible outer diskis attached to the adhesive patch assemblyby overmolding during the second shot of the aforementioned two-shot injection molding process.

The two-shot injection molding process is described in more detail in the flowchart of. The process can be performed using injection mold tooling (only the lower half 50 of which is shown in) having separate sets of mold cavities,for the hard and soft shots.

In step, the mold is closed (i.e., the upper and lower mold halves are brought together) in preparation for the first (hard) molding shot. This shot forms the rigid inner hubsof.

In step, molten plastic material is injected under pressure into the cavitiesto perform the hard shot. In the illustrated example, eight rigid inner hubsare formed simultaneously during the first molding shot.

In step, the mold is opened with the fully formed inner hubsretained in the upper half of the mold. The mold is then indexed by rotating the upper mold half by 180 degrees about a vertical axis with respect to the lower mold half. This aligns the upper mold cavities containing the fully formed inner hubswith the empty lower mold cavitiesin which the flexible outer diskswill be formed and overmolded with the rigid inner hubsin the second (soft) molding shot.

In step, robotic end-of-arm tools are used to place the adhesive patch assembliesinto the open mold cavitiesas shown in. The patch assembliesare oriented with their release linersfacing downwardly and the exposed surfaces of their adhesive patchesfacing upwardly into the mold cavity.

In step, the mold is again closed in preparation for the second (soft) molding shot. This shot forms the flexible outer disksof.

In step, the soft molding shot is performed by injecting molten plastic material into the mold cavitiesfrom gates (not shown) located beneath the patch assemblies. The holes,in the adhesive patchesand release linersare aligned with these gates. The molten plastic material passes through the holes,to form the flexible outer disksin overlying interlocked relationship with the previously formed rigid inner hubsas shown in(to facilitate the proper flow of the molten plastic material, it is preferred that the holes,be positioned so that they are at least partially unblocked relative to the hubs). At the same time, and with the assistance of the pressure under which the molten plastic material is injected into the mold during the soft shot, the molten plastic material impregnates or permeates the adhesive patchesby flowing into the many small interstices, openings or cavities that exist in the material of the patches. This creates a strong mechanical bond between the adhesive patchesand the flexible outer disksafter the injected plastic material has cooled and solidified, without the need for an adhesive. Depending on the specific materials used, a secondary bond can also be formed between the adhesive patchesand the rigid inner hubsduring the soft shot, thereby strengthening the connection between the adhesive patchesand the plastic central portionsgenerally. However, the primary bond is between the adhesive patchesand the flexible outer disks.

In step, the completed base assembliesare removed from the mold for further assembly and packaging steps. This includes the addition of the introducer needle hub, catheter, needle guardand related components that form the completed infusion setof.

It will be appreciated that the rotational indexing described in stepabove allows the two sets of mold cavities,to be operated simultaneously. This is done in a staggered manner so that hub-forming hard shots are performed on one side of the mold while disk-forming soft shots over previously-formed hubs are performed on the other side of the mold. It will also be appreciated that base assemblies for patch pumps and other types of on-body medical devices can be made using an injection molding process similar to that illustrated in.

In embodiments of the invention, the patch assemblycan be die-cut from commercially available 3M™ Medical Nonwoven Tape (Product No. 1776). In this product, the patch materialis a ˜11.5 mil (0.3 mm) thick white spunlace nonwoven tape made of randomly oriented polyester fibers, the skin-contact adhesiveis an acrylate adhesive developed for medical/surgical use, and the adhesive lineris 83 lb. poly-coated Kraft paper of 6 mil (0.15 mm) thickness with a silicone release layer on both sides. Another suitable material is 3M™ Single Coated, Extended Wear Nonwoven Medical Tape (Product No. 4076). Still other materials that can be used are various single-coated medical tapes that are available from the Medical Materials and Technologies division of 3M Company. Other types of fibrous, textured, perforated or porous materials that are able to withstand the heat and pressure of the injection molding process can also be used for the adhesive patchin the practice of the present invention.

In embodiments of the invention, the rigid inner huband flexible outer diskmay be made of any plastic materials that are suitable for injection molding. The rigid inner hubis preferably made from a polyester blended material or polycarbonate, although this is not required. The flexible outer diskis preferably made from a thermoplastic elastic material, some examples of which are listed in the table below Materials which allow for molding of the flexible outer diskat lower temperatures are preferred in order to avoid adverse effects on the skin contact adhesiveprovided between the patchand the release liner.

Although only a few embodiments of the present invention have been shown and described, the present invention is not limited to the described embodiments. For example, it may be possible to use compression molding for either or both of the molding steps, instead of injection molding. It will be appreciated by those skilled in the art that other changes may also be made to the disclosed embodiments without departing from the scope of the invention. In addition, any of the embodiments, features and/or elements disclosed herein may be combined with one another to form various additional combinations not specifically disclosed, as long as the embodiments, features and/or elements being combined do not contradict each other. All such changes and combinations are considered to be within the scope of the invention as defined by the appended claims and their equivalents.